Curved plate etching apparatus



Nov. 7, 1967 c. w. HOORNSTRA 3,351,077

CURVED PLATE ETCHING APPARATUS 2 Sheets-Sheet 1 Filed April 2, 1965 INVENTOR. C/oy/an Wf/oo/ms/ra Nov. 7, 1967 c. w. HOORNSTRA 3,351,077

CURVED PLATE ETCHING APPARATUS Filed April 2, 1965 2 Sheets-Sheet 3 INVENTOR C/ay/on W Hoarnsf/a United States Patent C) 3,351,077 CURVED PLATE ETCHING APPARATUS Clayton W. Hoornstra, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Apr. 2, 1965, Ser. No. 445,209 2 Claims. (Cl. 134-147) This invention relates to etching machines and particularly to a machine for etching plates which have an arcuate surface configuration.

So-called powderless etching has been used with notable success for many years in connection with the etching of flat plates.

Though a number of processes and machines exist which purport to produce a relief image of 'high quality on curved surfaces, none actually does so.

For example, when a printing cylinder or segment thereof having type and half-tone pictures photo-printed thereon is powderlessly etched by existing processes in existing machines, the typical result shows, to a greater or lesser degree, the following defects:

(1) Shoulder assymetry; the image shoulders in circumferential directions are inordinately broad while those in axial directions are inordinately narrow or are even entirely absent so that two sides of the images are actually under cut.

(2) Channeling; circumferential channels are etched into the bottom of the plate between image areas.

(3) A phenomenon known variously as tailing, run around, rundown or bleedoff in the vernacular of the trade; inordinately elongated shouldering occurs in circumferential directions from the boundaries of halftone image areas with nonimage areas.

When etching a plate by the powderless etching process, there will be relative motion or flow between the workpiece being etched and increments of a fluid medium adapted to remove material from the workpiece. The fluid medium will collide with the workpiece and with them flow across the surface of the workpiece because of ts momentum and/or the force of gravity before departing from the surface.

It has been found that the extent of excursion ofthe shoulder in any direction away from the margin of a relieved image element is directly proportional to the work done in moving increments of the fluid medium across said margin in that direction.

It can be appreciated that the etching of curved plates presents substantial problems in the achieving production of uniform shoulders in an image element. The

curved surface plus the force of gravity are factors which complicate the etching process.

Accordingly, a principal object of this invention is to provide an improved apparatus for making etchings on curved plates.

Another object of this invention is to provide an improved apparatus for etching image elements which have substantially uniform shoulders onto a curved plate.

A further object of this invention is to provide etching apparatus which may be used to produce etchings on a curved plate which are substantially free of channelmg.

Yet another object of this invention is to provide etching apparatus which'rnay be used to produce etchings on a curved plate which are substantially free of the phenomenon known variously as tailing, run-around, rundown, or bleedoff.

In accordance with this invention there is provided etching apparatus, comprising, within an enclosed chamher adapted to contain an etching bath, means for splashing material from said etching bath towards said curved plate, and a plate holding and moving mechanism which is adapted to cyclically vary the axial relationship between the longitudinal axis of the plate being etched and the surface of the etching bath while rotating said plate about its longitudinal axis.

The invention, as Well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is an isometric view, partly broken away to show detail, of an etching machine in accordance with this invention;

FIG. 2 is a fragmentary view of an alternative embodiment of a plate holding and moving mechanism in accordance with this invention, and

FIG. 3 is a schematic end view of an alternative embodiment of etching apparatus in accordance with this invention.

Referring to the drawing, there is shown etching apparatus, indicated generally by the numeral 10, which comprises an enclosed chamber 12 having splasher pad dles 1'4, 16, disposed on and coupled to shafts 18, 20, respectively. The shafts 18, 20 extend across the chamber 12 near the bottom thereof and are parallel with the bottom of the chamber. The shafts 18, 20 extend through the walls of the chamber 12, but bearings and seals arent shown for the sake of simplicity in the drawing. Gears 22, 24, whose teeth intermesh, are coupled to the end of the shafts 18, 20, respectively.

An electric motor 26 (or other suitable drive means) is coupled, via pulleys 30, 32 on the shaft 22 and motor shaft, respectively, and drive belt 28, to the shafts 18, 20.

A shaft 66 extends through one of the side walls 67 and is rigidly coupled to a generally U-shaped support member, indicated generally by the numeral 34. The support member 34 has a base element 36 and outwardly extending arms 38, 40. The arms 38, 40 are parallel to the shaft 66 and the base element 36- is perpendicular with respect to the shaft 66.

A workpiece holding mechanism 66, carrying a curved plate 62 to be etched, is coupled to a rotatable mandrel 42 which is journalled in suitable bearings 44, 46 near the outer end of the arms 40, 38, respectively. The end of the mandrel 42 which is near the arm 40 extends through the arm 40 and has a pulley 48 coupled thereto.

The shaft 66, journalled externally of the chamber 12 by bearings 69, 71, is a hollow shaft.

I An inner shaft 60 extends through the shaft 66. One end oft'he shaft 60 is coupled to the output gear box 84 of a drive motor 80. The other end of the gear 60' is coupled to a bevel gear 58 whose teeth engage the teeth .of a bevel gear 56. The gear 56 is rigidly coupled to a shaft 54 which is supported parallel and rotatably with respect to the support member 34, extending through the arm 40. A pulley 50 is coupled to the end of the shaft 54 which extends through the arm 40'. Belt means 52 couple the pulley 50 to the pulley 48 on the mandrel 42.

The longitudinal axis of the shaft 66 is perpendicular to the longitudinal axis of the paddle driving shafts 18, 20 and parallel to a plane passing through the shafts 18, 20.

A slotted arm 68 is rigidly coupled to the shaft 66 between the bearings 69,71. An oscillatory motion drive motor 73, supported'on a base 76, has a slotted arm '72 coupled to the output shaft of its gear box 82. A

or more rotations of the mandrel 42, the reversing means being in the control box 94, for example.

The motors, 80, 73 and bearings 69, 71 are rigidly coupled to a base plate 78 which is fixedly secured with respect to the side wall 67 of the chamber 12.

In operation, with the chamber 12 suitably filled with etchant bath to slightly above the bottom of the paddles 14, 16 (the depth the bath extends onto the paddles being desirably substantially equal along the length of the paddles), the motor 26 is operated to rotate the paddles 14, 16, thereby splashing the etchant bath material upwardly to impinge on the moving plate 62 to be etched.

With the motors 73, 80 in operation, the support member 34 carrying the mandrel 42 is oscillated back and forth with respect to the level of the etchant bath, the degree of oscillation being between 20 degrees and 90 degrees, but preferably about 40 degrees to 60 degrees. ()scillation occurs at a rate of 2 to 20 oscillations per minute, but preferably at a rate of 4 to 10 oscillations per minute.

Simultaneously with the oscillation of the support member 34, the shaft 60 causes the mandrel 42, and consequently the plate 62 to be etched, to rotate. Rotation of the mandrel is at a rate such that the peripheral speed of the plate 62 to be etched is between 70 and 250 feet per minute, and preferably 140-200 feet per minute. The reversal of direction of rotation of the mandrel may vary between zero and 60 times per minute, but preferably is between and 30 times per minute.

The amount of etchant bath thrown by the paddles will be known by those skilled in the powderless etching art.

FIG. 2 shows an alternative embodiment of etching plate movement mechanism. The shaft 104, corresponding to the shaft 66, has an elongated element 102 rigidly coupled perpendicularly with respect to its end which would extend into the chamber 12. An arm 110 is coupled perpendicularly with respect to the element 102 at one end of element 102, the arm 110 being parallel to the shaft 104. The base 106 and bearing 107 shown correspond to the plate 78 and bearing 71 in FIG. 1.

A shaft 112, inside the hollow shaft 104, is coupled via pulley 113, pulleys 116, 118 near the junction of the element 102 and arm 110, and pulley 119 coupled to a mandrel 122 which is rotatably supported from the outer end part of the arm 110.

The mandrel 122 carries and supports a plate 62a to be etched (by means of holding element 126 held in place on the mandrel 122 by bolt 124, for example).

A weight 108 coupled to or near the end of the element 102 which is remote from the arm 110, counter weights the element 102 to provide a balanced load to be oscillated by the shaft 104.

As may be seen, the oscillation of the plate 62a and its rotation about the mandrel 122 may be the same as in FIG. 1, though a different mechanism is used to achieve this motion.

FIG. 3 shows, in more or less schematic form, an end elevational view of etching apparatus in which a second pair of paddle elements are used. The apparatus includes the usual chamber 126, with etching bath 127 at the bottom part thereof with its level contacting the paddles 128, 130 which correspond generally with the paddles 14, 16 of FIG. 1.

The shafts 138, 140 extend through the side wall of the housing 126 (through seal 136) generally parallel to the level of the etchant bath, and correspond in function to the shafts 66, 60 respectively.

The V-shaped bracket 139, rigidly coupled to the shaft 138, corresponds to the support member 34 of FIG. 1. Pulleys 142, 146, 148 and belt 144 correspond to the pulley and belt arrangement of FIG. 2, for example.

The plate 152 to be etched is coupled to a mandrel 150 which is journalled in bearings 154, 156 and which is coupled to the pulley 148.

A second pair of paddles, 132, 134, corresponding in construction, for example, to the paddles 14, 16 of FIG. 1, are disposed substantially above but axially parallel to the first pair of paddles 128, 130.

The operation of the apparatus of FIG. 3, with respect to the paddles 128, 130, and the etching plate movement mechanism, is as described previously herein. However, especially when large plates are to be etched and/ or the oscillatory movement of the plate to be etched raises it a very substantial distance above the etchant bath, the socalled helper paddles help distribute further upwardly etchant bath thrown upwardly by the paddles 128, 130. The helper paddles 132, 134, thus provide means for more uniformly splashing the etching plate with etching bath material than is practicable when only a single set of paddles are used.

It is obvious that sprockets and chains may be substituted for the pulley and belt combinations illustrated. Materials of construction should be such that they are not adversely affected by nor do they adversely affect the etching bath. Temperature and other controls of the etching bath are known to those skilled in the powderless etching art and will not be detailed here.

Alternatively, a work holder which is rotatably mounted and driven with respect to a fixed mandrel may be substituted for the rotatable mandrel fixed work holder arrangements illustrated.

Normally, though not necessarily, the plate to be etched (or work piece) is mounted with the medial point of its axis of curvature at the medial point of the free portion of the mandrel about which it is carried. Preferably, the support member (34, for example) is configured to support the mandrel with the longitudinal axis of the mandrel intersecting the longitudinal axis of the oscillatory motion drive shaft (66, for example).

It should be noted, also, that the ends of the mechanical linkage element 70 may be locked in position along the slots of the arms 68, 70.

What is claimed is:

1. An etching machine which is useful for etching plates having arcuate surfaces, comprising means for holding a supply of etching bath material, means for applying said etching bath material against the surfaces to be etched, said means for holding a supply of etching bath material and means for applying etching bath material being enclosed in a chamber having a top and side walls, said means for applying etching bath material including a first array of paddles which contact said supply of etching bath material and a second array of paddles disposed above said first array of paddles, a plate holder having a longitudinal axis, said plate holder being mechanically transversely coupled to a drive shaft, said drive shaft extending through one of said side walls, means disposed externally of said chamber for rotating said shaft back and forth in a repetitive manner, and means for rotating said plate holder about its longitudinal axis as said drive shaft is rotated back and forth.

2. A machine in accordance with claim 1, wherein means are provided for rotating said paddles at a uniform rate with respect to each other.

References Cited UNITED STATES PATENTS 2,657,095 10/1953 James at al 134-194 XR 3,072,133 1/1963 Martz l34l94 XR 3,078,857 2/1963 Guenst 134-l93 XR 3,108,031 10/1963 Hasala et al. 13416lXR 3,122,150 2/1964 Henderson l34-147 XR CHARLES A. WILLMUTH, Primary Examiner.

R. L, BLEUTGE, Assistant Examiner. 

1. AN ETCHING MACHINE WHICH IS USEFUL FOR ETCHING PLATES HAVING ARCUATE SURFACES, COMPRISING MEANS FOR HOLDING A SUPPLY OF ETCHING BATH MATERIAL, MEANS FOR APPLYING SAID ETCHING BATH MATERIAL AGAINST THE SURFACES TO BE ETCHED, SAID MEANS FOR HOLDING A SUPPLY OF ETCHING BATH MATERIAL AND MEANS FOR APPLYING ETCHING BATH MATERIAL BEING ENCLOSED IN A CHAMBER HAVING A TOP AND SIDE WALLS, SAID MEANS FOR APPLYING ETCHING BATH MATERIAL INCLUDING A FIRST SPRAY OF PADDLES WHICH CONTACT SAID SUPPLY OF ETCHING BATH MATERIAL AND A SECOND ARRAY OF PADDLES DISPOSED ABOVE SAID FIRST ARRAY OF PADDLES, A PLATES HOLDER HAVING A LONGITUDINAL AXIS, SAID PLATE HOLDER BEING MECHANICALLY TRANSVERSELY COUPLED TO A DRIVE SHAFT, SAID DRIVE SHAFT AXIALLY IN A FORWARD DIRECTION WHILE WIRE IS COILED THEREON AS A HELIX AND IN THE OPPOSITE DIRECTION WHILE THE WIRE HELIX RECOILS, MECHANISM FOR ROTATING THE ARBOR AT A CONTROLLED RATE IN ONE DIRECTION FOR COILING THE WIRE AS A HELIX THEREON, AN ASSOCIATED MECHANISM FOR ROTATING THE ARBOR IN THE OPPOSITE DIRECTION AT A CONTROLLED AND SLOWER RATE AND THEREBY CONTROLLING THE RATE OF RECOIL OF THE HELIX AND A CAM CONTROLLED FORMING TOOL OPERATED IN A TIMED RELATION WITH THE RECOIL ROTATION OF THE ARBOR. 